Topic summary
24 karat
Extracted from the Wikipedia article Fineness.
Various ways of expressing fineness have been used and two remain in common use: millesimal fineness expressed in units of parts per 1,000 and karats or carats used only for gold. Karats measure the parts per 24, so that 18 karat = 18⁄24 = 75% gold and 24 karat gold is considered 100% gold.